Car was overheating goin slow or at idle I changed the thermostat twice, cooling relay, then fans wasn't coming on, got new fans and there coming on now but not turning off I unplug them so the battery wouldnt die. Any ideas why there not turnin off now?

The aftermarket fan was defective I returned it an got manufacturer ford fan solved the overheating problem. Went ahead an flushed my coolant and put motorcraft 50/50 back in, but now the car just seems louder than normal, the rpm isn't high but it sounds like it is expecially when going down a hill, just sounds like it's trying so hard but only have this problem when going down hill or pushing the gas, any ideas? Or is it something I should even be worried about?